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Abstract:

The present invention relates to a ceramic composition and a porous
ceramic insulating material comprising the same, which is widely used as
a core material in sandwich panels or fire doors. The ceramic composition
comprises 44-60 wt % of glass powder, 8-15 wt % of fly ash, 4-8 wt % of
intercrete as a surface treatment agent, and 23-29 wt % of water glass.
The porous ceramic insulating material manufactured from the composition
is lightweight and is an environmentally friendly material which
generates no toxic gas when it catches fire. The ceramic insulating
material can be produced at a low temperature of 800˜900°
C., and thus has low production cost. In addition, it can be continuously
manufactured in a sheet form.

6. A porous ceramic insulating material, which comprises the ceramic
composition of claim 1 and has a specific gravity of 0.3-0.5 g/cm3,
a flexural strength of 40 Kgf/cm2 or less, a thermal conductivity of
0.1-0.14 W/mK, and a flame retardance of grade 1.

7. A method for manufacturing a porous ceramic insulating material
comprising the ceramic composition set forth in claim 1, the method
comprising the steps of: mixing the components of said composition to
obtain a mixture; drying and powdering the mixture to obtain a powdered
material; heat-treating the powdered material so as to be calcined and
foamed; molding the heat-treated material into a predetermined shape;
cooling the molded material; and cutting and finishing the cooled
material.

8. The method of claim 7, wherein the heat-treatment step is carried out
at 800.about.900.degree. C. for 20 minutes to 3 hours.

9. The method of claim 7, wherein, in the step of mixing the components
of the composition, germanium (Ge) is further added in addition to said
glass powder, fly ash, intercrete and water glass.

10. A method for manufacturing a porous ceramic insulating material
comprising the ceramic composition set forth in claim 2, the method
comprising the steps of: mixing the components of said composition to
obtain a mixture; drying and powdering the mixture to obtain a powdered
material; heat-treating the powdered material so as to be calcined and
foamed; molding the heat-treated material into a predetermined shape;
cooling the molded material; and cutting and finishing the cooled
material.

11. A method for manufacturing a porous ceramic insulating material
comprising the ceramic composition set forth in claim 3, the method
comprising the steps of: mixing the components of said composition to
obtain a mixture; drying and powdering the mixture to obtain a powdered
material; heat-treating the powdered material so as to be calcined and
foamed; molding the heat-treated material into a predetermined shape;
cooling the molded material; and cutting and finishing the cooled
material.

12. A method for manufacturing a porous ceramic insulating material
comprising the ceramic composition set forth in claim 4, the method
comprising the steps of: mixing the components of said composition to
obtain a mixture; drying and powdering the mixture to obtain a powdered
material; heat-treating the powdered material so as to be calcined and
foamed; molding the heat-treated material into a predetermined shape;
cooling the molded material; and cutting and finishing the cooled
material.

13. A method for manufacturing a porous ceramic insulating material
comprising the ceramic composition set forth in claim 5, the method
comprising the steps of: mixing the components of said composition to
obtain a mixture; drying and powdering the mixture to obtain a powdered
material; heat-treating the powdered material so as to be calcined and
foamed; molding the heat-treated material into a predetermined shape;
cooling the molded material; and cutting and finishing the cooled
material.

Description:

TECHNICAL FIELD

[0001] The present invention relates, in general, to a ceramic
composition, a porous ceramic insulating material comprising the same and
a manufacturing method thereof, and more particularly, to a ceramic
composition comprising 44-60 wt % of glass powder, 8-15 wt % of fly ash,
4-8 wt % of intercrete and 23-29 wt % of water glass, and to a porous
ceramic insulating material comprising the composition and a
manufacturing method thereof.

BACKGROUND ART

[0002] Recently, efforts have been made to reduce energy consumption and
greenhouse gas emissions. In this respect, in order to reduce energy
consumption in the building sector accounting for about 30% of total
energy consumption in Korea, studies on novel compositions and insulating
materials comprising the same have been actively conducted.

[0003] Insulating materials are used to minimize the transfer of heat and
can be broadly divided into organic insulating materials and inorganic
insulating materials. In Korea, inorganic insulating materials account
for about 70% of insulating materials, and inorganic insulating materials
are frequently used in applications requiring flame retardant materials.

[0004] Table 1 below summarizes various insulating materials and the
properties, workability and toxicity of each insulating material.

[0005] Referring to Table 1, in the glass wool that is a typical inorganic
insulating material, the sealed air layer between the glass fibers
provides insulation. The glass wool is noncombustible and absorbs sound,
and the effective thickness and insulation property of are not decreased
by compression. However, it absorbs water, making it needed to provide a
separate damp-proof layer, and gives a tingling feeling to workers.

[0006] The polystyrene that is an organic insulating material has a high
insulation effect, is lightweight and is easy to use. However, it is weak
against UV rays, and is likely to generate toxic gases, which are fatal
to the human body, when it catches fire.

[0007] In addition, the polyurethane that is another organic insulating
material has shortcomings in that the volume and thermal conductivity
thereof are reduced after application thereof and in that it is likely to
generate toxic gases when it catches fire.

[0008] Among insulating materials which are used as core materials in
sandwich panels or fire doors, organic insulating materials have
excellent insulation properties, but are weak against fire. Due to this
problem, these organic insulating materials have no commercial value or
are used in limited applications. In addition, inorganic insulating
materials have a problem in that they require high-temperature processes,
which increase process costs.

[0009] Meanwhile, methods of manufacturing ceramic insulating materials
using ceramic compositions include a foaming method, which uses gel
casting and double emulsion, and a foaming method which uses fly ash,
clay and the like as main materials and calcium carbonate (CaCO3)
and carbon as foaming agents. Porous insulating materials manufactured by
such methods have porous structures which vary depending on the
composition of raw materials, physical properties such as particle size,
and the kind and content of foaming agent.

[0010] In addition, there is a double-calcination method which uses waste
glass as a main material and iron trioxide (Fe2O3) as a foaming
agent and in which calcination is repeated to form open pores. A porous
insulating material manufactured by this method has small pores.

[0011] However, these methods have problems in that specific materials are
used in large amounts or a temperature of 1000° C. or higher is
generally required, except for modified processes comprising
pressurization.

DISCLOSURE

Technical Problem

[0012] It is an object of the present invention to provide a ceramic
composition and a porous ceramic insulating material comprising the same,
in which the ceramic composition has closed pores while maintaining the
characteristic function of the ceramic material, and thus has improved
properties, including lightweight, insulating and flame retardant
properties, and is harmless to the human body and environmentally
friendly.

[0013] Another object of the present invention is to provide a method for
manufacturing a porous ceramic insulating material, the method employing
a low-temperature heat-treatment process which reduces the production
cost of the insulating material and enables the production of large
amounts of the insulating material.

[0015] The present invention also provides a porous ceramic insulating
material, which comprises said ceramic composition and has a specific
gravity of 0.3-0.5 g/cm3, a flexural strength of 40 Kgf/cm2 or
less, a thermal conductivity of 0.1-0.14 W/mK, and a flame retardance of
grade 1.

[0016] The present invention also provides a method for manufacturing a
porous ceramic insulating material, the method comprising the steps of:
mixing the components of said composition to obtain a mixture; drying and
powdering the mixture to obtain a powdered material; calcining and
foaming the powdered material in a heat-treatment furnace at
800-900° C. for 20 minutes to 3 hours; naturally cooling the
molded material; and cutting and finishing the cooled material according
to its intended use.

Advantageous Effects

[0017] A porous ceramic insulating material comprising a ceramic
composition according to the present invention has advantages of low
specific gravity, low thermal conductivity and excellent flame
retardance. In addition, the ceramic insulating material is an
environmentally friendly material which generates no toxic gas when it
catches fire. Moreover, it can be produced at a low temperature of
800˜900° C., and thus has low production cost. In addition,
it can be continuously manufactured in a sheet form.

[0018] The porous ceramic insulating material manufactured by the method
of the present invention has a specific gravity of 0.3-0.5 g/cm3, a
flexural strength of 40 Kgf/cm2 or less, a thermal conductivity of
0.1-0.14 W/mK, and a flame retardance of grade 1.

DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a photograph showing ceramic insulating materials
manufactured from various compositions having different component ratios.

[0020] FIG. 2a shows the results of analyzing the components of glass
powder in a ceramic composition according to one embodiment of the
present invention.

[0021] FIG. 2b shows the results of analyzing the components of fly ash in
a ceramic composition according to one embodiment of the present
invention.

[0022] FIG. 2c shows the results of analyzing the components of intercrete
in a ceramic composition according to one embodiment of the present
invention.

[0023]FIG. 3 is a flow diagram showing a process of manufacturing a
porous ceramic insulating material using a ceramic composition according
to the present invention.

MODE FOR INVENTION

[0024] Hereinafter, the present invention will be described in further
detail with reference to the accompanying drawings.

[0026] In example 1 in FIG. 1, a ceramic insulating material was
manufactured from a composition according to the present invention. In
example 2, a ceramic insulating material was manufactured from a
composition containing no intercrete, and in example 3, a ceramic
insulating material was manufactured from a composition containing 25 wt
% of fly ash. Meanwhile, in example 4, a ceramic insulating material was
manufactured from a composition containing no intercrete and 29 wt % of
fly ash.

[0027] In examples 1, 2 and 3, 8 wt % of germanium (Ge) was added in order
to increase the strength of the ceramic material.

[0028] As can be seen in FIG. 1, only the ceramic insulating material
manufactured from the composition of the present invention has a
relatively low water absorption rate, a low thermal conductivity of 0.181
W/mK and a low specific gravity of 0.533 g/cm3, suggesting that it
is lightweight and, at the same time, has excellent insulation effects.

[0029] In order to manufacture the ceramic material of example 1, which
has a suitable porosity and contains closed pores having a suitable size,
the contents of glass powder, fly ash, intercrete and water glass should
be within suitable ranges. In this case, it is possible to manufacture a
porous ceramic insulating material, which satisfies the objects of the
present invention and has low production cost and improved properties,
including lightweight, insulating and flame-retardant properties.
Specific reasons why the contents of the components should be in the
ranges specified in the present invention will now be described.

[0030] The glass powder that is used in the present invention may be not
only plain glass powder, but also waste glass powder. The glass powder
functions to lower the softening temperature of the composition so that
the composition can be foamed at a relatively low temperature. In
addition, it functions to improve and maintain the strength of the
ceramic material.

[0031] In the composition of the present invention, the glass powder is
preferably used in an amount of 44-60 wt % based on the total weight of
the composition. If the content of the glass powder is less than 44 wt %,
the pore size of the ceramic material will decrease while the density
will increase, and if the content of the glass powder is more than 60 wt
%, the surface of the ceramic material will become glassy and the
composition will be excessively foamed.

[0032] The fly ash that is used in the present invention is a byproduct of
coal combustion and is in the form of fine powder which is collected in a
dust collector. It is a typical pozzolanic material, and produces a
compound that acts like cement at room temperature, when it is bonded
with calcium carbonate and meets water. Currently, fly ash has excellent
properties for use as a cement replacement.

[0033] In the present invention, the fly ash is preferably used in an
amount of 8-15 wt % based on the total weight of the composition. If the
content of the fly ash is less than 8 wt %, the composition will be
excessively foamed while the strength will decrease, and if it is more
than 15 wt %, the foaming of the composition will be significantly
inhibited while the pore size will decrease and the density will
decrease.

[0034] The intercrete that is used in the present invention is used mainly
as a cement setting accelerator. The components of the intercrete is
similar to those of the glass powder that is used as the main material in
the present invention, but the content of calcium carbonate (CaO) thereof
is slightly higher than that of conventional glass powder. The intercrete
is used to smoothen the surface of the foamed material.

[0035] The intercrete functions to improve the surface smoothness of the
foamed material, and thus it has the effect of reducing the generation of
waste in the cutting and finishing steps when a sheet-like material
having a large volume is to be manufactured. In the present invention,
the intercrete is preferably used in an amount of 4-8 wt % based on the
total weight of the composition.

[0036] If the content of the intercrete is less than 4 wt %, the surface
layer of the ceramic material will swell up in the foaming step, and thus
in the case of a sheet-like foamed material having a large volume, the
generation of waste in the cutting step will increase, resulting in an
increase in the production cost. If the content of the intercrete is more
than 8 wt %, the smoothness of the foamed material will not further
increase and the production cost will be increased due to the excessive
use of the intercrete.

[0037] The water glass that is used in the present invention is an
inorganic compound which is most widely used among water-soluble
silicates. It is soluble in water. Examples thereof include compounds of
alkali metals and silicon dioxide (SiO2) at various molar ratios,
including sodium silicate, potassium silicate and lithium silicate, which
have a water content of about 10-30%. The water glass is made by melting
high-purity sand with sodium carbonate (Na2CO3) or potassium
carbonate at 1100˜1200° C.

[0038] In the present invention, the water glass is preferably used in an
amount of 23-29 wt % based on the total weight of the composition. If the
content of the water glass is less than 23 wt %, the foaming of the
composition will decrease so that the weight of the composition will
increase, and if it is more than 29 wt %, the composition will be
excessively foamed so that the surface of the ceramic material will
become glassy.

[0039] FIGS. 2a, 2b and 2c show the results of analyzing the components of
each of glass powder, fly ash and intercrete in a ceramic composition
according to one embodiment of the present invention.

[0043]FIG. 3 is a flow diagram showing a process of manufacturing a
porous ceramic insulating material using a ceramic composition according
to the present invention. As shown in FIG. 3, the inventive method for
manufacturing the porous ceramic insulating material comprises a mixing
step S310, a drying and powdering step S320, a heat-treatment step S330,
a cooling step S340 and a cutting and finishing step S350.

[0045] In the drying and powdering step S320, the mixture is dried and
powdered.

[0046] In the heat-treatment step S330, the powdered material is calcined
and foamed. In this step, calcination and foaming can be performed at a
low temperature of 800˜900° C., and thus the production cost
can be reduced.

[0047] In the cooling step S340, the molded material is cooled. Herein,
the cooling is preferably natural cooling, but when a large amount of the
ceramic material is produced, forced air cooling may also be carried out
at a specific temperature or lower in order to reduce the drying time,
thus reducing the total process time.

[0048] In the cutting and finishing step S350, the dried material is cut
and finished according to the intended use. A large sheet-like material
(950×650 mm) can be continuously manufactured and can be used as a
core material in various products.

[0049] Until now, research and development similar to the present
invention has been performed in various areas, including the academic
world, but the developed molded materials are still in the research stage
and are mostly laboratory-scale samples having a small volume. Moreover,
even if molded materials having a large volume were developed, they had
low pore size uniformity for various reasons, particularly the
non-uniform properties of each of the raw materials.

[0050] For example, if thorough tracking of the place in which a mineral
is produced is not performed, the uniformity of the properties of a
product comprising the mineral cannot be guaranteed.

[0051] The present inventors have performed the thorough tracking of each
raw material and have made extensive efforts to find a method of managing
the properties of each raw material and to determine the most suitable
conditions (e.g., the content of each raw material, and heat-treatment
temperature) while experiencing a lot of trial and error, and as a
result, could manufacture a molded material having a large volume by a
continuous manufacturing process. Thus, a basis for producing a large
amount of a porous ceramic insulating material could be established
according to the present invention.

[0052] As described above, according to the manufacturing method of the
present invention, a porous ceramic insulating material can be
manufactured, which has closed pores and shows excellent properties,
including lightweight, insulating and flame-retardant properties. In
addition, a large sheet-like insulating material can be manufactured by a
continuous process.

[0053] Although the preferred embodiments of the present invention have
been disclosed for illustrative purposes, those skilled in the art will
appreciate that various modifications, additions and substitutions are
possible, without departing from the scope and spirit of the invention as
disclosed in the accompanying claims.